1. Field of the Invention
The present invention relates generally to security monitoring systems and, more particularly, to a security monitoring system in which a video frame from video surveillance cameras is selected for transmission to a remote monitoring station based on a set of predetermined criteria.
2. Prior Art
Security monitoring systems of the prior art, particularly residential security systems, typically utilize a box that monitors contact sensors for doors and windows and one or more infra-red sensors for area monitoring. When a contact is triggered or an infra-red sensor triggers, an alarm is sounded and a signal is sent via a data link such as a phone line to a central monitoring site. The central monitoring site typically initiates a set of phone calls, to the homeowner, to work, and/or to a designated neighbor to determine if the alarm signal was due to an unauthorized intruder or just to an accidental triggering by a family member or other authorized occupant of the structure.
If the alarm signal cannot be resolved by the phone calls, it is passed to the local police department. According to the International Association of Chiefs of Police (www.theiacp.org), alarm calls comprise 10% to 30% of police calls, and 94% to 98% of the calls turn out to be xe2x80x9cfalse alarmsxe2x80x9d in the sense that they were not due to an unauthorized intruder.
Significant portions (over 70%) of xe2x80x9cfalse alarmsxe2x80x9d are caused by what is referred to as exit/entrance conflicts. For instance, in the situation of a residential alarm system, the homeowner or other authorized occupant of a residence often arms the security system while leaving the residence and shortly thereafter realizes that they have forgotten something in the residence. As they return to the residence, they enter without disarming the system thereby causing an alarm to be sounded and/or an alarm signal to be sent to a central monitoring site. Similarly, the homeowner may arm the security system and remain inside the residence, such as during the night and may thereafter leave to get something outside the residence, e.g., the morning paper, thereby triggering a false alarm.
In view of the prior art, there is a need for a security monitoring system, which resolves these and other types of entry/exit conflicts.
Therefore it is an object of the present invention to provide a security monitoring system which reduces the number of false alarms inherent in the prior art security monitoring systems.
It is a further objective of the present invention to provide a security monitoring system which transmits image data to a remote monitoring station for inspection by the monitoring staff to determine if an alarm is a true or false alarm.
It is yet another objective of the present invention to provide a security monitoring system which selects a portion of the image data to the remote monitoring station based upon a set of predetermined criteria such that the bandwidth for transmitting the image data is not exceeded.
Accordingly, a security monitoring system is provided. The security monitoring system comprises: an alarm system having means for detection of an alarm in a structure; at least one camera for capturing image data inside and/or outside the structure; a processor for selecting a subset of the image data upon the occurrence of the alarm based on a set of predetermined criteria; and transmission means for transmitting the subset of image data to a remote location.
Preferably, the at least one camera is a video camera, the image data is video image data, and the subset of the image data is at least one video frame of the video image data. The transmitted image data should be such as to allow a monitoring operator to quickly decide if the alarm is a true alarm or a false alarm. More preferably, the processor ranks each video frame from the image data according to how well each video frame meets a set of predetermined criteria which evaluate how useful they are to a monitoring operator in distinguishing false/true alarms, and the transmission means transmits a predetermined number of video frames having the best rank to the remote location.
One approach to transmitting image data to the remote location is to simply transmit the frame at the time of the alarm, or a set of frames corresponding to some time interval around the alarm time (e.g., transmit an image taken 0.5 seconds before the alarm, at the alarm and 0.5 seconds after the alarm). However, such a scheme is not guaranteed to catch the cause of the alarm, and even if the cause is caught, it may not be portrayed in a form quickly interpretable by the monitoring operator (e.g., the image may catch the heel of an intruder departing through a doorway).
In preferred implementations of the security monitoring system of the present invention, the processor subtracts an established background from each video frame resulting in a difference region. The predetermined criteria that evaluate how useful the image is to a monitoring operator are selected from a group consisting of: how centered the difference region is in the video frame; how large the difference region is in the video frame; whether the difference region consists of a large difference region or a group of smaller difference regions in the video frame; the contrast of the difference region in the video frame; the lighting condition on the difference region in the video frame; and whether a face is detected in the difference region in the video frame. If the predetermined criteria includes whether a face is detected in the difference region of the video frame, further predetermined criteria are preferably selected from a group consisting of: how much of the face is visible in the video frame; whether the face is turned towards of away from the video frame; and whether key features of the face are visible in the video frame.
In alternative implementations of the security monitoring system of the present invention, the predetermined criteria are selected from a group consisting of: whether the video frame is blurred; how much skin color is contained in the video frame; if a person is recognized in the video frame; and the lighting condition on a region of motion in the video frame.
In yet another preferred implementation of the security monitoring of the present invention, the system further comprises: an image recording system for recording the image data to be analyzed by the computer vision system wherein the image data is recorded for a predetermined time period before and after the occurrence of the alarm; an analog to digital converter for converting analog image data to digital image data prior to being analyzed by the processor; and a compression means for compressing the subset of the image data prior to transmission to the remote location.
Also provided are methods for security monitoring of a structure having the security monitoring system of the present invention.